Known problems with (E)VLA and VLBA archival data

This page was last updated on 2012 Jan 24 14:45 MST to keep track of known problems that affected data taken with the VLA/EVLA and/or the VLBA that appears and is remaining either in the data archive, or in the programs reading the data archive into the data reduction packages. For current problems that are affecting current data, and thus also are not fixed in the data archives and data readers, check the EVLA returns page!
By the way, if your data is from after ... 2005, checking the EVLA returns page regularly is a good idea anyway..

Note that you may have good data that appears to have problems. Over the years bugs have been discovered and corrected in AIPS. Please make sure you have a reasonably recent version of AIPS, especially if you are dealing with data during the period of transition from VLA to EVLA. The same holds for the CASA (formerly AIPS++) data reduction package.

Unfortunately this page remains a work in progress as new and old issues are found continuously. Of course if you know of an unlisted problem (which isn't unlikely as we've just started this page from our faded memories), suspect one, or have another question please contact the NRAO Helpdesk using your my.nrao.edu login.

Use these links to skip the introduction and jump to the list of (E)VLA or VLBA archive issues directly.

Introduction, or how to read this page

The following figure shows an example of a time line of three specific issues. The header on top shows the time line labeled in years. The first column contains an issue number that corresponds to issue numbers in the (long) listing below. To asses your data, find the appropriate (VLA or VLBA) time line below and draw a vertical line at the date of your data. Check each issue number for which your line crossses the corresponding issue line (and also the ones that start just after..). To be conservative, the lines include the whole month in which the issue appears; check the issue descriptiton for the exact dates and times.

'01 '02 '03 '04 '05 '06 '07 '08 '09 '10 '11 '12

21

20

19

For example, if you download data from 2006, you need not to look at issue number 21, 20, nor 19. However, if your data is from 2008 you need to check issue #21 and can ignore issues #20 and #19. Similarly, if your data is from the end of 2002, you can skip issue #21 but need to study issue #19. And because issue #20 has been found just after your data was taken, it might be a good idea to check issue #20 too as is may be in your data and we don't know about it (in which case you should contact us through the NRAO Helpdesk using your my.nrao.edu login)!

Known problems are listed in reverse issue number, which over due time will become a random order of (approximate) starting date, separated for (E)VLA and VLBA issues (some may be listed under both if applicable). However, as some issues may not be related to the data, but to the data readers themselves, you may want to read the general reader (FILLM or FITLD) issues first. If your data includes EVLA antennas (as may be the case after ... 2005), you should also check the EVLA returns page.

Now that you have your list of specific issues you have to check, you should do the following; remember that the time line is conservative in that it includes whole months, and that you also might be interested in issues that start just after your vertical data line.

If your data is from before the red "Begin" date or after the green "End" date, you should be fine for the specific issue listed. Also if you download any data after the blue "Archive fixed?" date, you should not be affected anymore by that specific issue. More exact begin and end times on the dates are given in the section describing the issue, which you can get at by clicking the link.

If your data is from between the red "Begin" and the green "End" date, and you obtained the data before the blue"Archive fixed?" date (either from an archive download, an on-line FILLM, or by any other means such as from your collaborator ...), your data may be affected! Because specific issues may only affect certain data, the "Notes" column should indicate under which circumstances the data is affected. Note that the "Archive fixed?" column is only given for the purpose of determining whether you should pay attention to the issue description below; it is not intened to give you a clue about whether we will (or even can) fix the archive or not if it says "not fixed".

The flow diagram on the right hand side of this page should help to determine how to deal with a specific issue; click on the image for a more readable version.

(E)VLA archive issues: (for VLBA see below)

  #  |    2001    |    2002    |    2003    |    2004    |    2005    |    2006    |    2007    |    2008    |    2009    |    2010    |    2011    |    2012    |
      JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 
 ----|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|
1010 |            |            |            |            |            |            |            |            |            |            |           =|=           |
1009 |            |            |            |            |            |            |            |            |            |            |        ====|            |
1008 |            |            |            |            |            |            |            |            |            |            |      =     |            |
1007 |            |            |            |            |            |            |            |            |            |            |      =     |            |
1006 |            |            |            |            |            |            |            |            |            |            |    =       |            |
1004 |            |            |            |            |            |            |            |            |            |    =       |            |            |
1002 |            |            |            |            |            |            |            |            |           =|============|====>       |            |
1003 |            |            |            |            |            |            |            |            |           =|============|====>       |            |
1001 |            |            |            |            |            |            |            |            |     ===>   |            |            |            |
 019 |            |            |            |            |            |            |            |            |            |  ==========|====>>      |            |
 018 |            |            |            |            |            |            |            |            |     =======|=           |            |            |
 017 |            |            |            |            |            |          ?=|============|============|============|            |            |            |
 016 |            |            |            |            |            |            |            |            |          = |            |            |            |
 015 |            |            |            |            |            |            |            |            |  =         |            |            |            |
 003 |            |            |            |            |            |            |            |            |===         |            |            |            |  
 004 |            |            |            |            |            |            |            |  ?==       |            |            |            |            |  
 005 |            |            |            |            |            |            |            |=           |            |            |            |            |  
 009 |            |            |            |            |            |            |        =   |            |            |            |            |            |  
 006 |            |            |            |            |            |            |      ==    |            |            |            |            |            |  
 008 |            |            |            |            |            |            |     ===    |            |            |            |            |            |  
 007 |            |            |            |            |            |            |     ===    |            |            |            |            |            |  
 002 |            |            |            |            |            |            |     ==     |            |            |            |            |            |  
 014 |            |            |            |            |            |            |     =======|============|============|==>>        |            |            |
 013 |            |            |            |            |            |            |     =======|============|??          |            |            |            |
 011 |            |            |            |            |            |    ??======|============|====        |            |            |            |            |  
 012 |            |            |            |            |            |    ??======|===         |            |            |            |            |            |  
 001 |            |            |            |            |            |    ??==    |            |            |            |            |            |            |  
 010 |============|============|============|============|============|============|======      |            |            |            |            |            |
 

  #  |    1989    |    1990    |    1991    |    1992    |    1993    |    1994    |    1995    |    1996    |    1997    |    1998    |    1999    |    2000    |
      JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 
 ----|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|
 010 |============|============|============|============|============|============|============|============|============|============|============|============|
  
 

  #  |    1977    |    1978    |    1979    |    1980    |    1981    |    1982    |    1983    |    1984    |    1985    |    1986    |    1987    |    1988    |
      JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 
 ----|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|
 010 |============|============|============|============|============|============|============|============|============|============|============|============|

General AIPS FILLM (and FILLR) issues
Check the EVLA returns page, last updated on 2012 January 24
Specific (E)VLA archive issues:
	#	Begin	End	Archive fixed?	Issue (follow links)	Notes

	001	2006 Jul/Aug		not fixed	First EVLA antennas
	002	2007 Jun 28	2007 Jul 29	fixed	Wrong u,v, and w coordinates	TWO separate issues
	003	2009 Jan 14	2009 Mar 08	not fixed	Timing error	Data taken on Fri (UT)
	004	2008 Mar/Apr	2008 May	not fixed	Online flagging
	005	2008 Jan 04	2008 Jan 24	not fixed	IAT clock error
	006	2007 Jul 30	2007 Sep 20	2008 Apr 22	Sideband issue	All line data
	007	2007 Jun 28	2007 Aug 21	not fixed	System Temperature	Antennas 11 and 19
	008	2007 Jun 29	2007 Aug 29	not fixed	Pointing error	Antennas 1 to 9
	009	2007 Sep 14	2007 Sep 19	2007 Sep 24	Frequency increment
	010	1979 Jun	2007 Jun 29	not fixed	(u,v,w) error
	011	2006	2008 Apr 09	not fixed	Doppler tracking	EVLA antennas
	012	2006	2007 Mar 02	not fixed	Mozaicing error	EVLA antennas
	013	2007 Jun 27	2008 ??	not fixed	25 MHz BW problem
	014	2007 Jun 27		not fixed	12.5 MHz noise
	015	2009 Mar 10	2009 Mar 19	not fixed	Phase jumps	EVLA antennas
	016	2009 Nov 17	2009 Nov 20	not fixed	Tsys/Timing error
	017	2006 Dec	2009 Dec 18	not fixed	Wrong Doppler calculations	dynamic time (J)observe files
	018	2009 Jun 17	2010 Jan 10	not fixed	Wrong Tsys in Ka band	7 of the Ka antennas
	019	2010 Mar 01	not yet	not fixed	Bad Stokes V
	1001	2009 June 17	2009 fall		CASA	importasdm fails
	1002	2009 Dec 31		not fixed	Scans missed
	1003	2009 Dec 31		not fixed	BDFs missing
	1004	2010 May 22	2010 May 25	not fixed	Bad data
	1006	2011 May 15	2011 May	not fixed	Clock problem
	1007	2011 Jul 28	2011 Aug 01	not fixed	No SysPower	(not essential)
	1008	2011 Jul 07	2011 Jul 11	not fixed	Unstable IFs B,C
	1009	2011 Sep 20	2011 Dec 02	not fixed	CBE integration failed	For Tint > 1 sec
	1010	2011 Dec 23	2012 Jan 12	not fixed	Weather data	Opacity corrections

VLBA archive issues:

  #  |    2001    |    2002    |    2003    |    2004    |    2005    |    2006    |    2007    |    2008    |    2009    |    2010    |    2011    |    2012    |
      JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 
 ----|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|
 504 |            |            |            |            |            |            |            |            |        === |            |            |            |
 501 |            |            |            |            |            |            |            |=           |            |            |            |            |
 502 |            |            |         ===|============|========    |            |            |            |            |            |            |            |
 503 |            |            |    ========|============|========    |            |            |            |            |            |            |            |
 

  #  |    1989    |    1990    |    1991    |    1992    |    1993    |    1994    |    1995    |    1996    |    1997    |    1998    |    1999    |    2000    |
      JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 
 ----|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|------------|

General AIPS FITLD issues
Specific VLBA archive issues:
	#	Begin	End	Archive fixed?	Issue (follow links)	Notes

	501	2008 Jan 04	2008 Jan 18	not fixed	Weather table
	502	2003 Q4	2005 Aug 15	fixed 2005 Aug 15	Phased Array Sensitivity	Phased array only
	503	2003 May	2005 Aug 08	not fixed	EOP errors
	504	2009 Sep 21	2009 Nov 26	fixed 2010 Jan 03	AN file error	preprocessed archive files only

AIPS task FILLM issues:


Occasionally coding updates to FILLM introduced bugs.
Problem start: 1970
Problem fixed:
Archive fixed:
Workaround: Not readily available; reload data.
Last update: Monday, 09-Mar-2009 11:30:41 MDT by L.O. Sjouwerman
Please read the AIPS letter or check the AIPS AIPS patches. Alternatively search the history of the current version (CHANGE.DOC) for FILLM to see if you are affected. If so and you have an old version of AIPS, please reinstall a more recent version or if you are current, run the MidNightJob
Back

1 : EVLA antennas included in the array.


First few EVLA antennas in the array.
Problem start: 2006 July/August
Problem fixed:
Archive fixed:
Workaround: For problems with the first few EVLA antennas, delete the data taken with these 1-3 antennas.
Last update: Friday, 24-Apr-2009 15:45:42 MDT by L.O. Sjouwerman
As of 1 August 2006, all regular observing programs were given the EVLA antennas that had returned to operations (earlier for test programs). They are expected to give reasonable data most of the time, but the early days of the transition may have introduced bad performance or unexpected artifacts at the few EVLA antennas in the array. Probably the best and easiest solution is to delete the few visibilities observed with these antennas. Note that the EVLA antennas prior to the C array of 2006 have no antenna positions.
Back

2 : Post-MODCOMP uvw errors


New control software calculated u,v, and w coordinates wrongly.
Problem start: 2007 June 28
Problem fixed: 2007 July 5
Archive fixed: 2007 August 1
Workaround: Reload data from the archive or run UVFIX on the data.
Last update: Friday, 01-May-2009 15:12:51 MDT by L.O. Sjouwerman
This item relates to TWO similar issues in this time range The MODCOMP computers that have run the VLA for many years were replaced by the EVLA monitor and control system on June 28, 2007. We have discovered that from that time until July 5, 18:20 UT, the u's v's and w's were written to the VLA data archive with the wrong sign. The data in the archive were corrected on July 10, 16:00 UT. A problem with the online calculation of negative u's, v's, and w's has been discovered for all data taken since the VLA's MODCOMP computers were replaced by the EVLA monitor and control system on June 27, 2007. All astronomical projects observed between June 28, 2007, 09:00 UT, and August 1, 2007, 23:45 UT, are affected. (Note that this problem is separate from the uvw sign error that affected data between June 28 and July 5.) Projects affected: AB1233, AB1239, AB1245, AB1246, AB1248, AB1251, AB1254, AB1256, AB1257, AB1278, AC856, AC874, AC879, AC888, AD562, AF452, AF456, AG744, AG745, AG753, AG756, AH939, AJ337, AK634, AK656, AL693, AL698, AM889, AM902, AM904, AM910, AN129, AR637, AR638, AR642, AR646, AS887, AS899, AS903, AS911, AT342, AT343, AT345, AW703, AY178, BB240, BC173, S8398, S8463, S8531, S8723, STUDE1, STUDE2
Back

3 : Timing error


EOP applied incorreclty
Problem start: 2009 January 14
Problem fixed: 2009 March 08
Archive fixed:
Workaround: (algorithm currently investigated) Make-up observations have been arranged.
Last update: Thursday, 23-Apr-2009 17:33:38 MDT by L.O. Sjouwerman
The VLA observations below were afflicted with a time error of about a second, due to improper application of the Earth Orientation Parameters. A time-correction scheme with the AIPS task CLCOR is not yet available, but may eventually become available (the archive data will not be fixed). Affected data: StartIATDate-Time Code 2009-03-01 00:00 AM978 2009-02-28 23:06 AM978 2009-02-28 21:05 AB1301 2009-02-28 20:06 AR685 2009-02-28 19:36 AB1321 2009-02-28 09:37 SA598 2009-02-28 07:38 AM975 2009-02-27 19:40 AE172 2009-02-21 21:03 ST001 2009-02-20 17:07 AB1314 2009-02-14 17:01 AH984 2009-02-14 16:31 AB1321 2009-02-14 11:58 AW743 2009-02-14 00:04 AG807 2009-02-13 23:33 AB1321 2009-02-13 22:03 AG807 2009-02-07 22:58 AB1320 2009-02-07 12:00 AK706 2009-02-06 23:01 AB1320 2009-01-31 13:27 AR687 2009-01-31 09:28 AM941 2009-01-30 20:28 AR685
Back

4 : Online flagging erratic


Online flagging not always properly applied
Problem start: 2008 March/April
Problem fixed: yes
Archive fixed: not fixed
Workaround: Carefull inspection of data
Last update: Thursday, 23-Apr-2009 16:47:27 MDT by L.O. Sjouwerman
During one day in March 2008 and a three-day period in April 2008, online flagging was not always applied in all cases. The most common effect is that antennas did not always get flagged while slewing between scans. We recommend particular care while inspecting and editing data taken in those time intervals. Projects potentially affected by online flagging problems. Dates and times in UT. Project Date begin end Project Date begin end AG778 March 6 05:44 07:43 AM932 March 6 07:43 08:42 AM932 March 6 10:12 12:42 AR661 March 6 12:42 14:41 AM932 March 6 14:41 17:11 AE165 April 15 23:32 04:32 AS929 April 16 04:32 05:02 AS945 April 16 05:02 06:01 AE165 April 16 06:01 11:00 AH967 April 17 08:27 15:56 BM257 April 17 15:56 16:26 AB1285 April 18 00:25 09:23 AH868 April 18 09:23 10:53 AR642 April 18 10:53 11:53 AW710 April 18 11:53 12:53 AR642 April 18 12:53 13:52 AR642 April 18 14:22 15:22 AT360 April 18 15:22 21:21
Back

5 : IAT clock error


A clock timing error
Problem start: 2008 January 4
Problem fixed: 2008 January 24
Archive fixed: not fixed
Workaround: Project segments have been reobserved; or disregard EVLA antennas.
Last update: Friday, 24-Apr-2009 15:38:48 MDT by L.O. Sjouwerman
An error occurred in the setting of the clock that drives the VLA antennas and the VLA correlator, affecting all astronomical data obtained between Jan 4, 02:18 IAT, and Jan 7, 18:04 IAT, and on Jan 24 (during AH927). The time error was sufficiently small (~50 ms) that the effect on VLA observations is negligible. However, the EVLA antennas, which do not use that clock, were out of sync with respect to the VLA correlator during that time interval. The effect of this out-of-sync condition is that: - VLA-EVLA baselines have reduced sensitivity and calibration difficulties - EVLA-EVLA baselines have very large (~100%) closure errors For most purposes, the EVLA antennas will be unusable. The overall effect on your data will be a loss in sensitivity. Projects potentially affected by this: Jan 4 - Jan 7: AD574, AH884, AH927, AK678, AL695, AR642, AR650, AS887 Jan 24: AH927
Back

6 : Conjugated phases


Incorrect sideband being set for certain spectral line projects
Problem start: 2007 Jul 30
Problem fixed: 2007 Sep
Archive fixed: 2008 Apr 22
Workaround: Reload data from the archive or inspect data and use FLOPM with OPCODE'VLAE'
Last update: Thursday, 23-Apr-2009 17:20:53 MDT by L.O. Sjouwerman
For a limited time period during July-September 2007 the incorrect sideband information was occasionally being set by the VLA correlator for certain spectral line projects. The resulting effect on data is that the direction of the frequency labelling was reversed, and the phases were conjugated. A table of the dates/times affected is given below, and one or more of your observations were compromised by this problem. We are working on fixing the data in the online archive, but it will take a few weeks to complete. If you have already started processing your data there is a new AIPS task FLOPM, available in the frozen 31DEC07 version of AIPS, and in the development 31DEC08 version. Specifying OPTYPE='VLAE' will reverse the frequency labelling and conjugate the phases. The time range of data to be corrected must also be specified explicitly. Projects, frequencies, and IAT dates/times affected by frequency labelling and phase conjugation problem: AF456, X band: Jul 30 from beginning to end (C band is OK) AC856, L band: Sep 09 from 17:34:15.8 to end AC882, 4&P bands: Sep 01 from beginning to end AF440, L band: Sep 04 from 15:34:22.5 to 15:51:21 AK664, C band: Sep 07 from 05:46:32.5 to end AM889, L band: Aug 23 from 13:58:01.7 to end Aug 26 from beginning to 10:01:28 Sep 06 from 13:29:01.7 to 13:32:01 and from 14:00:01.7 to end Sep 12 from 11:54:51.7 to end AR659, L band: Sep 20 from 04:56:11.7 to end
Back

7 : Incorrect system temperature


Nominal sensitivity and system temperature wrong for antennas 11 and 19
Problem start: 2007 June 28
Problem fixed: 2007 August 21
Archive fixed: not fixed
Workaround: Reload data using a patched FILLM
Last update: Thursday, 23-Apr-2009 17:36:45 MDT by L.O. Sjouwerman
For data taken between June 27 and August 21 antennas 11 and 19 had an incorrect nominal sensitivity and system temperature stored with the archival data. This can be identified by zeroes for the system temperature in plots of Tsys in the TY table using SNPLT. Unfortunately AIPS has not been calculating the weights for these antennas correctly when loading the data using FILLM. A patch dated September 28, 2007, is available for the 31DEC06 version of AIPS that handles this correctly. For the 31DEC07 version of AIPS, a midnight job run on September 22, 2007, or later is needed. You will need to update your version of AIPS and reload your data to obtain the correct weights for the affected antennas. Any flagging that has already been carried out is probably fine and FG tables can be copied directly to the new dataset using TACOP. Alternatively, if you already have fully calibrated data in a single source file, you can run WTMOD on that file with: NOISE=1; NOISE(11)=1/3; NOISE(19)=NOISE(11) Projects that may have been affected: AB1233, AB1239, AB1245, AB1246, AB1248, AB1250, AB1251, AB1254 AB1256, AB1257, AB1258, AB1278, AC843, AC856, AC874, AC879, AC881 AC884, AC888, AC908, AC909, AD562, AD565, AF452, AF456, AG744, AG745 AG752, AG753, AG756, AG757, AG777, AH939, AH941, AJ337, AK634, AK656 AL693, AL696, AL698, AL703, AM889, AM902, AM904, AM910, AN129, AO219 AO223, AR637, AR638, AR642, AR646, AS887, AS897, AS899, AS903, AS911 AS925, AT342, AT343, AT345, AU119, AW705, AY178, S8531
Back

8 : Pointing errors


Pointing solutions not applied to antennas 1-9
Problem start: 2007 June 29
Problem fixed: 2007 August 29
Archive fixed: not fixed
Workaround: Not available.
Last update: Thursday, 23-Apr-2009 17:40:37 MDT by L.O. Sjouwerman
It was discovered that between the dates of June 27, 2007, and August 29, 2007 inclusive, reference pointing solutions were not being applied to antennas numbered 1 through 9. The effect on your data will be the following: 1) Pointing offsets may be different for your absolute flux calibrator from your phase calibrator and target source. Make sure you exclude antennas 1-9 when bootstrapping flux calibration using GETJY in AIPS, otherwise the absolute flux calibration will be highly uncertain. 2) The overall sensitivity may be somewhat lower than expected. 3) Extended sources may suffer from poor image fidelity if antennas with poor pointing are included. Projects that may have been affected: AB1233, AB1251, AB1258, AC843, AC879, AC884, AC888, AD565, AF452, AF454, AH941, AH942, AK634, AK656, AL698, AL703, AL704, AM910, AO219, AR642, AS887, AS897, AT342, AT343, AY178, BC173
Back

9 : Incorrect VLA headers


Incorrect frequency increment for spectral line data
Problem start: 2007 September 14
Problem fixed: 2007 September 19
Archive fixed: 2007 September 24
Workaround: Reload data from the archive.
Last update: Friday, 24-Apr-2009 15:34:07 MDT by L.O. Sjouwerman
Due to an error in the EVLA online system, spectral line data taken between September 13, 2007, and September 18, 2007, had incorrect increments on the frequency axis. Rather than reporting the channel width it instead reported the total bandwidth, or in some circumstances, 50 MHz. This should be evident by running IMHEAD in AIPS. Possibly affected: Sept-14 AF454 Sept-15 AF454, AR659, AM909, AC879 Sept-16 AC879, AR659, AB1280 Sept-17 AC910, AM909 Sept-18 AR659
Back

10 : Pre-MODCOMP uvw errors


MODCOMP VLA control computers (pre-EVLA) calculated u,v, and w coordinates wrongly.
Problem start: 1979 June
Problem fixed: Not fixed
Archive fixed: Not fixed
Workaround: Run UVFIX on the data.
Last update: Friday, 01-May-2009 15:12:51 MDT by L.O. Sjouwerman
The MODCOMP computers that have run the VLA for many years were calculating the uvw's wrongly. While the uvw errors are small they are affecting long time baseline astrometry and/or astromomy attempted between data on both sides of the switch from MODCOMP to EVLA control computers on 2007 June 27. This appears as a rotation on the sky between the two epochs.
Back

11 : Phase jumps while Doppler tracking


Doppler tracked observations show phase jumps on EVLA antennas
Problem start: 2006
Problem fixed: 2008 April 09
Archive fixed: Not fixed
Workaround: Not available; discard EVLA data.
Last update: Friday, 24-Apr-2009 16:30:46 MDT by L.O. Sjouwerman
It seems that possibly ALL observations on the EVLA (including those done before turning off the Modcomps) for which the sky frequency of the target and calibrator are not the same (as is common for doppler-tracked observations) suffer from phase jumps meaning that the target cannot be properly calibrated. Projects affected - any using EVLA antennas. The list below is only complete for projects after 2007 June 27, but observations prior to that date may also suffer from this even if not listed here: Date Project Frequency Antennas used 20070811 AA314 4.8284 GHz 16 VLA 9 EVLA 4 OUT 20070903 AA314 6.6666 GHz 0 VLA 10 EVLA 19 OUT 20070811 AA314 6.6667 GHz 0 VLA 9 EVLA 20 OUT 20070811 AA314 6.6667 GHz 16 VLA 9 EVLA 4 OUT 20070818 AB1250 1.6123 GHz 16 VLA 10 EVLA 3 OUT 20070927 AB1258 22.2271 GHz 15 VLA 11 EVLA 3 OUT 20071004 AB1258 22.2281 GHz 15 VLA 11 EVLA 3 OUT 20071005 AB1258 22.2319 GHz 15 VLA 11 EVLA 3 OUT 20070921 AB1258 22.2363 GHz 15 VLA 11 EVLA 3 OUT 20070824 AB1258 22.2403 GHz 16 VLA 10 EVLA 3 OUT 20070810 AB1258 6.6689 GHz 16 VLA 9 EVLA 4 OUT 20070816 AB1258 6.67 GHz 16 VLA 10 EVLA 3 OUT 20071116 AC0904 6.6668 GHz 0 VLA 12 EVLA 17 OUT 20071101 AC0904 6.6673 GHz 0 VLA 12 EVLA 17 OUT 20071031 AC0904 6.6677 GHz 0 VLA 12 EVLA 17 OUT 20070708 AC856 1.6653 GHz 15 VLA 9 EVLA 5 OUT 20070921 AC888 22.2289 GHz 15 VLA 11 EVLA 3 OUT 20070921 AC888 42.8088 GHz 15 VLA 11 EVLA 3 OUT 20070921 AC888 43.1102 GHz 15 VLA 11 EVLA 3 OUT 20080127 AC904 6.6677 GHz 0 VLA 13 EVLA 16 OUT 20080126 AC904 6.6677 GHz 13 VLA 13 EVLA 3 OUT 20070917 AC910 1.6117 GHz 15 VLA 11 EVLA 3 OUT 20070917 AC910 1.6119 GHz 15 VLA 11 EVLA 3 OUT 20070917 AC910 1.6653 GHz 15 VLA 11 EVLA 3 OUT 20071202 AF440 1.6121 GHz 14 VLA 12 EVLA 3 OUT 20070906 AF440 1.6123 GHz 15 VLA 11 EVLA 3 OUT 20071213 AF465 22.2336 GHz 14 VLA 12 EVLA 3 OUT 20070810 AH941 18.5042 GHz 0 VLA 10 EVLA 19 OUT 20070924 AI123 6.1165 GHz 15 VLA 11 EVLA 3 OUT 20071123 AK0680 22.2337 GHz 14 VLA 12 EVLA 3 OUT 20071123 AK0680 6.6671 GHz 0 VLA 12 EVLA 17 OUT 20071124 AK0680 6.667 GHz 0 VLA 12 EVLA 17 OUT 20070901 AL704 24.1424 GHz 16 VLA 10 EVLA 3 OUT 20071217 AL707 21.3013 GHz 14 VLA 12 EVLA 3 OUT 20071215 AL707 45.2868 GHz 14 VLA 12 EVLA 3 OUT 20080126 AP500 1.7214 GHz 13 VLA 13 EVLA 3 OUT 20071005 AP500 1.7215 GHz 15 VLA 11 EVLA 3 OUT 20080128 AP529 4.8348 GHz 13 VLA 13 EVLA 3 OUT 20071113 AS660 22.2342 GHz 14 VLA 12 EVLA 3 OUT 20071112 AS660 22.2346 GHz 14 VLA 12 EVLA 3 OUT 20071222 AS800 42.8255 GHz 14 VLA 11 EVLA 4 OUT 20071130 AS858 1.612 GHz 14 VLA 12 EVLA 3 OUT 20070801 AS911 1.6655 GHz 16 VLA 10 EVLA 3 OUT 20070731 AS911 1.7206 GHz 16 VLA 10 EVLA 3 OUT 20070729 AS911 1.7206 GHz 16 VLA 9 EVLA 4 OUT 20070627 AW3H2 4.8306 GHz 17 VLA 10 EVLA 2 OUT 20070627 AW3OHB 6.6699 GHz 0 VLA 10 EVLA 19 OUT 20071207 AY184 6.6679 GHz 0 VLA 12 EVLA 17 OUT 20071003 BM272 22.2334 GHz 15 VLA 11 EVLA 3 OUT 20071008 BM272 22.2341 GHz 15 VLA 11 EVLA 3 OUT 20071005 BM272 22.2353 GHz 15 VLA 11 EVLA 3 OUT
Back

12 : Mozaic mode not working for EVLA


Mozaic mode not working for EVLA antennas
Problem start: 2006
Problem fixed: 2007 March 2
Archive fixed: not Fixed
Workaround: Not readily available; disregard EVLA data.
Last update: Friday, 24-Apr-2009 16:42:42 MDT by L.O. Sjouwerman
Mozaic mode did not work for EVLA antennas prior to 2007 March 2
Back

13 : DC offset in 25 MHz line mode


DC offset in 25 MHz line mode
Problem start: 2007 June 27
Problem fixed: Fixed?
Archive fixed: Not fixed
Workaround: Not readily available. Use AIPS tasks
Last update: Friday, 24-Apr-2009 16:41:26 MDT by L.O. Sjouwerman
The correlator controller caused a DC offset in 25 MHz spectral line mode, since September 26, 2006 (Supposedly this was fixed by turning off self-test for all 25 MHz observations)
Back

14 : High noise in 12.5 MHz bandwidth mode


High noise in 12.5 MHz line mode
Problem start: 2007 June 27
Problem fixed: Not fixed - discouraged 12.5 MHz observing until WIDAR arrives
Archive fixed: Not fixed
Workaround: Not readily available; do not use for observations until WIDAR.
Last update: Friday, 24-Apr-2009 16:42:36 MDT by L.O. Sjouwerman
The correlator controller introduces a high noise in 12.5 MHz spectral line observations - do not use 12.5 MHz bandwidth.
Back

15 : Random phase jumps


Phase jumps appear on EVLA antennas
Problem start: 2009 March 10
Problem fixed: 2009 March 19
Archive fixed: Not fixed
Workaround: Not available. Affected projects were reobserved.
Last update: Monday, 27-Apr-2009 10:07:27 MDT by L.O. Sjouwerman
A kernel upgrade to our central time servers caused them to miscalculate internal clock drift. Over the course of a day their clock error became greater than the 20ms acceptable limit causing a phase jump problem on EVLA - EVLA and EVLA - VLA baselines (the EVLA antennas have phase jumps). The phase jumps generally occur on most or all EVLA antennas at the same times. The times of the jumps are random, and can occur at the few per hour rate; although about once per hour or so is more typical, and there are possibly longer periods of data that are not affected. All data between Mar 10, UT 13:00 and Mar 19, UT 09:00, is affected. Projects were reobserved.
Back

16 : Tsys/timing problem


A timing error has corrupted system temperature values
Problem start: 2009 November 17
Problem fixed: 2009 November 20
Archive fixed: Not fixed
Workaround: See below.
Last update: Thursday, 26-Nov-2009 11:14:59 MST by L.O. Sjouwerman
From 12:00 MST on November 17, 2009, through approximately 17:00 on November 20, 2009, there was a timing error on one of the computers at the VLA site that resulted in bad values of the system temperature being passed through the online system to archival data. If you load your data using FILLM in AIPS scaling by the nominal sensitivity (the default) your data will be corrupted. You must load your data in raw correlation coefficients in FILLM by setting DOWEIGHT = 1 CPARM(2) = 2048 (see the help file for FILLM for further details). The use of raw correlation coefficients makes the data more susceptible to gain variations as a function of elevation, and care should be taken to try to match the elevation for flux density bootstrapping. We apologise for this inconvenience. Please let us know if you have any further questions about your data. Projects affected: AB1323 AD613 AM991 AR700 AC963 AF484 AP570 AS992 AD612 AK718 AR699 CALSUR
Back

17 : Doppler tracking with *.obs files in dynamic time


Doppler correction was calculated for the wrong date
Problem start: 2006 ~December
Problem fixed: 2009 December 18
Archive fixed: Not fixed
Workaround: See below.
Last update: Friday, 01-Jan-2010 12:02:41 MST by L.O. Sjouwerman
Dear PI, We have recently discovered that Doppler-tracked data observed in the VLA dynamic queue are Doppler tracked by the new EVLA online system to the LST date in the header of the submitted observe file, rather than the date of observation. If no date appears in the header the online system uses the date of observation. In extreme cases a spectral line may be shifted entirely out of the requested passband of the VLA, but at the very least lines will likely appear at the wrong velocity if processed in the normal way by AIPS. Scheduling blocks created by the OPT are not affected. You may use the online DOPSET tool at http://www.vla.nrao.edu/astro/guides/dopset/, specifying first the LST date in the observe file and then that of the observation, to find out the expected frequency shift. For data processed by AIPS the correct Doppler tracking must be derived offline. The precise steps depend on the version of AIPS used. For AIPS versions 31DEC09 or later the fix can be done using either the multisource file or a calibrated and SPLIT single-source file. Make sure to download the frozen version of 31DEC09 or run the midnight job to obtain the latest updates before loading your data using FILLM. For AIPS versions 31DEC08 or earlier (or 31DEC09 versions obtained prior to the 31DEC09 code freeze) the multisource file must be used. Multi-source file: in most cases the source (SU) table will have the requested source velocity, rest frequency, velocity type, frame definition, and velocity reference pixel already set by FILLM, it's just that the observed topocentric frequencies are not consistent with these values for the date of observation. All that needs to be done is to run CVEL, applying the bandpass calibration if this has not already been done, to resample the data onto the requested velocity axis. Note that if there are multiple frequency (FQ) IDs each FQID will have to be processed separately. If for any reason the velocity information is not in the SU table, SETJY can be used to set it prior to running CVEL. Single-source file: use CVEL to specify the velocity parameters using APARM(1)-(6), and run to resample the data onto the new velocity axis. If your spectral line is strong and spectrally undersampled you may see Gibbs ringing in the output spectrum following CVEL. In this case you should consider using Hanning smoothing to suppress the ringing. Data processed by CASA will be labelled with the correct velocity, since CASA interpolates onto the requested velocity axis from the observed topocentric frequencies of date, and does not rely on the velocity information provided by the online system. The data do undergo some spectral smoothing in this process. This Doppler tracking problem applies to EVLA antennas included in all dynamically observed projects from the beginning of 2006 December onwards. Observe files requesting Doppler tracking submitted to the dynamic queue as of December 18, 2009 have already been processed by NRAO staff to remove the LST date/time from the header. Projects potentially affected: AA320 AA329 AB1258 AB1316 AC826 AC888 AC904 AC910 AF459 AF460 AF465 AF483 AG810 AH1003 AH941 AH991 AI123 AI128 AI135 AJ352 AK664 AM874 AM912 AM914 AM974 AM981 AR676 AS884 AS909 AS911 AS983 AW711 AW760 AY184 AY191 AY196 AZ186 BM257 BM272 BR145 ST002 ST003
Back

[an error occurred while processing this directive] [an error occurred while processing this directive]

1001 # : CASA


importasdm (not really an EVLA issue)
Problem start: 2009 June 17
Problem fixed: (sometime fall)
Archive fixed: no fix needed
Workaround: Reload data.
Last update: Friday, 09-Dec-2011 12:08:45 MST by L.O. Sjouwerman

Back

1002 # : Scans missed


Some scheduled scans were not observed
Problem start: 2009 December 31
Problem fixed: Intemittently recurring
Archive fixed: not fixed
Workaround: Not readily available.
Last update: Friday, 09-Dec-2011 12:06:14 MST by L.O. Sjouwerman

Back

1003 # : BDFs missing


Some expected BDFs were not created
Problem start: 2009 December 31
Problem fixed: Intermittently recurring
Archive fixed: not fixed
Workaround: Not readily available.
Last update: Friday, 09-Dec-2011 12:04:25 MST by L.O. Sjouwerman

Back

1004 # : Bad data


EVLA system problems
Problem start: 2010 May 22
Problem fixed: 2010 May 25
Archive fixed: not fixed
Workaround: Not readily available.
Last update: Friday, 09-Dec-2011 12:02:37 MST by L.O. Sjouwerman

Back

1006 # : Clock problem


Problem with clock signals, data corrupted
Problem start: 2011 May 15
Problem fixed: 2011 May
Archive fixed: not fixed
Workaround: Not readily available.
Last update: Friday, 09-Dec-2011 12:01:09 MST by L.O. Sjouwerman

Back

1007 # : No SysPower


System Power table missing
Problem start: 2011 July 28
Problem fixed: 2011 August 1
Archive fixed: not fixed
Workaround: Calibrate without (correlator coefficients).
Last update: Friday, 09-Dec-2011 11:35:28 MST by L.O. Sjouwerman
This period the System Power information was not included in the data, but previously it was not either and not suggested for improved calibration - it is not essential (but helps to have it).
Back

1008 # : Data acquisition problems


Severe amplitude variations IFs B and C
Problem start: 2011 July 7 (16:52 UT)
Problem fixed: 2011 July 11 (21:46 UT)
Archive fixed: not fixed
Workaround: Apply switched power corrections
Last update: Friday, 09-Dec-2011 11:29:04 MST by L.O. Sjouwerman
Not all projects were affected but those that were had severe amplitude variability on IFs B and C and would need correction to be usable.
Back

1009 # : CBE integration failed


Correlator only averaged for a single second every tick mark
Problem start: 2011 September 20
Problem fixed: 2011 December 3
Archive fixed: No fix possible
Workaround: Not readily available; data will have reduced sensitivity by Sqrt(Tint)
Last update: Friday, 09-Dec-2011 11:27:32 MST by L.O. Sjouwerman
The CBE (correlator back-end) averages visibilities over some time interval. With the start of wideband observations in D-array 2011 it was suggested to increase it to e.g. 3, 5 or 10 seconds (depending on your science case) to keep the output data set sizes relatively small. However, only one second of data ended up in each of the 'averaged' visibilities. The effect is that the time on source is reduced by a factor of the integration time, and thus the effective 'theoretical' RMS noise a factor Sqrt(Tint) higher than expected. Elegible projects will be offered make-up time as much as possible.
Back

1010 # : Opacity corrections


weather station
Problem start: 2011 December 23, 19:12 UT
Problem fixed: 2012 January 12, 23:37 UT
Archive fixed: N/A
Workaround: Use seasonal model only
Last update: Tuesday, 24-Jan-2012 14:48:21 MST by L.O. Sjouwerman
From 23 December 2011, 19:12 UT to 12 January 2012, 23:37 UT the weather station located on the EVLA site failed to produce reliable data. This has consequences for the zenith opacities systems such as CASA and AIPS derive. During the time interval above these zenith opacities should be based on the seasonal model only instead of a weighted average of actual weather data and the seasonal model. This can be accomplished as follows: AIPS - delete version 1 of the CL table, and create a new version 1 by running the task INDXR with BPARM(1)=0 and BPARM(10)=-1. CASA - derive the zenith opacity by running the contributed task plotWX with seasonal_weight=1.0. For more information on plotWX see http://casaguides.nrao.edu/index.php?title=CASA_EVLA_Scripts
Back

AIPS task FITLD issues:


Occasionally coding updates to FITLD introduced bugs.
Problem start: 1970
Problem fixed:
Archive fixed:
Workaround: Not readily available; reload data.
Last update: Monday, 09-Mar-2009 11:30:20 MDT by L.O. Sjouwerman
Please read the AIPS letter or check the AIPS AIPS patches. Alternatively search the history of the current version (CHANGE.DOC) for FITLD to see if you are affected. If so and you have an old version of AIPS, please reinstall a more recent version or if you are current, run the MidNightJob
Back

501 : Incorrect weather tables


Weather tables scrambled
Problem start: 2008 January 04
Problem fixed: 2008 January 18
Archive fixed:
Workaround: Not readily available; reload data.
Last update: Monday, 09-Mar-2009 14:26:07 MDT by L.O. Sjouwerman
The weather tables were not parsed correcly and are not usable in, e.g., APCAL.
Back

502 : Phased array sensitivity


Array not recognized as phased array
Problem start: 2003 Q4
Problem fixed: 2005 August 15
Archive fixed: 2005 August 15
Workaround: See below
Last update: Monday, 09-Mar-2009 15:06:47 MDT by L.O. Sjouwerman
The sensitivities for the phased VLA in the experiments below may be off from expected. Single dish VLA observations should not be affected. Probably affected experiments, in alphabetical order: bb190, bb191, bb191b, bb196, bb204, bb209a, bd103, bf083, bf084a, bf084b, bg141, bg150, bg155, bh128, bj054, bk114b, bk114e, bl121, bm223a, bm223b, bn032, br088c, br092a, br092b, br092c, br092d, br102a, br102b, br102c, bu030a, bu030b, bu030c, bw076, bw080, bw084, gb049a, gb049b, gb049c, gb053, gd017a, gd017b, gd018, gg049a, gm048c, gm055a, gm059a, gt005, ty001 Probably unaffected: bk110, bk114a, bk114c, bk114d, bk119, bn031, bt075, tf029a (as they probably need to run ANTAB to get the VLA TY values included) To recognize whether you are affected, look in your data's TY-table: Figure out the antenna number for the VLA using PRTAN or TYPE ANTNUM('Y') Then check if for antenna Y, the phased VLA and for the phased VLA only, the 8th and 10th (TANT 1, TANT 2, assuming you have both polarizations) columns are set to -1.0 (or any other negative value, which will be true only if you run ANTAB). Note that if there are no TANT values in the TY table for the antenna number corresponding with the VLA, you need to run ANTAB anyway and you will not encounter this problem. Use for example AIPS> default prtab; docrt 1; inext 'ty'; box 4 8 10 AIPS> indisk i; getname j; go prtab (and many returns until you get to the antenna number for the VLA) If the columns are filled with a negative value, you should have nothing to worry about. If they are labeled 'INDE' for the phased VLA, please read on. Since late-2003 we have included the gain curve and Tsys values for the VLA in most VLBA distribution tapes in order to make it more convenient for our users; i.e. not to have to run ANTAB anymore and have the VLA behave just as a VLBA antenna as much as possible. However, for the phased VLA, the FITLD/VLBALOAD program did not recognize whether the VLA was used in single dish or in phased array mode. This means that for the phased VLA, the Tsys/Tant values were not properly converted into proper SN table gain values in APCAL/VLBACALA, unless you used ANTAB to (re)load the VLA Tsys values. To get a proper Tsys value, APCAL/VLBACALA uses the TANT columns of the TY table to see if it is supposed to extract the source flux from the SU table in order to convert the given Tsys/Tant in the TY table, and store the appropriate gain solutions in the newly generated SN table. To solve for the problem, unfortunately you probably have to recalibrate your data from the start. If you haven't started loading the data from the distribution tape(s) yet, you may want to fetch todays (15 Aug 2005) new FITLD version using the midnight job (MNJ). If you got your data using the archive ftp method, let me know and in a day or two there will be a new file for you to download. Or you can still load the data into AIPS using the old FITLD and/or archive file and follow the fix below. If you have your data on disk inside AIPS, the easiest fix is as follows: - delete (maybe after a TASAV) all SN and CL tables except for CL#1 - find the antenna number for Y (eg with task PRTAN) - use TABED, with: default tabed; indisk i; getname j inext 'TY'; optype 'repl'; keyvalue=-1,0; outdisk=indisk aparm=8,0,0,2,4,[antenna number of phased VLA]; go tabed and once more for a second polarization with: aparm(1)=10; go tabed - rerun VLBACALA or ACCOR/APCAL, etc
Back

503 : Earth Orientation Parameter errors


Wrong EOP parameters were used in the corrlation
Problem start: 2003 May
Problem fixed: 2005 Aug 08
Archive fixed:
Workaround: Run CLCOR on the affected data.
Last update: Monday, 09-Mar-2009 14:49:33 MDT by L.O. Sjouwerman
A significant issue has been found with the Earth Orientation Parameters (EOP) used in VLBA correlator job scripts since May 2003. The problem adversely affects projects that depend on an accurate correlator model. Such projects include any that use phase referencing or that try to solve for the atmosphere using sources scattered around the sky. Projects that depend primarily on self calibration on the target source or that use the total delays from the correlator are not affected. A bug was found in the correlator job generator that caused it to use predicted values of EOP rather than measured rapid service values. The magnitude of the errors, mostly in UT1-UTC, is roughly equivalent to having source position errors of typically about 10 mas before June 2004 and about 20 mas since then. The worst cases were about 4 times these values. The effect on phase referenced observations depends on details of the offsets and geometry. The phase error on a source depends on position on the sky and on time. To first order, corrections based on calibrator observations will fix the phases on a target. But, as with any other geometry error, the residual error on the target after calibration will be approximately the calibrator phase error reduced by the calibrator to target separation in radians (typically well under 0.1). This phase residual can shift measured positions. But it not completely equivalent to a position shift so it can also degrade phase reference image dynamic range and, in extreme cases, can prevent detection of the target. To fix the data use the new CLCOR capability, included in the 31DEC05 version of AIPS 9and later) and be sure that it has been updated (midnight job) since 2005 September 30. To read the VLBA Test Memo, go to http://www.vlba.nrao.edu/memos/test/ and click on the type (ps, pdf, html) of file you would like to read for Memo 69. The job generator was fixed on August 8, 2005. There is currently no AIPS program that can correct the affected data sets. But soon the capability will be added as an option in CLCOR. Note that even without this bug, VLBA correlation is based on rapid service EOP values from close to the date of observation, not on the finals that are only available much later. Users wanting high accuracy may wish to make corrections for any observations.
Back

504 : AN file error in preprocessed files


FITLD assigned the wrong sign to BY when antennas were added to AN
Problem start: 2009 September 21
Problem fixed: 2009 November 26
Archive fixed: 2010 January 03
Workaround: Inspect AN file and reverse BY coordnate if necessary.
Last update: Monday, 04-Jan-2010 09:02:10 MST by L.O. Sjouwerman
FITLD would change the sign of By in the antennas file for all antennas which did not occur in the first input IDI-format file. The sign of By is correct for all antennas that occurred in that first file. FITLD is run on preprocessed files and this error thus does not affect data loaded by a FITLD compiled (with a MNJ) outside the dates above.
Back

[an error occurred while processing this directive]

Modified on 2012-Jan-24 by L.O. Sjouwerman